In an electric charging system, an electric charger and an electric vehicle is connected via a charging cable, and charging power is provided to a battery of the electric vehicle via the charging cable. The electric charger calculates a voltage drop based on a supply current Is of the electric charger and an electric resistance of the charging cable. The electric charger compares a supply voltage of the electric charger with a determination value, and, if the supply voltage reaches the determination value, determines that the battery is charged to a fully-charged state. The determination value is updated by adding the voltage drop to a preset determination base value so as to take the voltage drop of the charging cable into account.
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1. An electric charging system that connects an electric charger and an electric vehicle via a charging cable and charges an electric storage device mounted on the electric vehicle, the electric charging system comprising:
an electric charger, comprising:
a power converter configured to convert AC power received from an external power source to DC power, and comprising a positive electrode and a negative electrode electrically connected to two power supply lines, respectively,
a supply-side voltage sensor connected to the two power supply lines and configured to detect supply voltage values,
a charging controller comprising a supply-side processor communicable with a vehicle controller mounted on the electric vehicle and the supply-side voltage sensor, and
a housing accommodating the power converter, the supply-side voltage sensor, and the charging controller, and provided outside of and separately from the electric vehicle; and
a charging cable comprising:
a free edge including power supply connectors electrically connected to the power converter with the two power supply lines, the power supply connectors being connectable to charging connectors of the electric vehicle,
a fixed edge fixed to the housing, and
an elongated portion extended between the free edge and the fixed edge, and provided outside of and separately from the electric vehicle;
wherein the supply-side processor is configured to:
when the power supply connectors are connected to charging connectors of the electric vehicle, cause the electric charger to supply the DC power to the electric vehicle through the charging cable at detected supply voltage values, cause the electric vehicle to receive the DC power at receiving side voltage values, and receive the detected supply voltage values from the supply-side voltage sensor;
generate detected supply voltage data indicating a change of the detected supply voltage values with respect to time;
generate processed supply voltage data by subjecting the detected supply voltage data to a filtering process;
when the power supply connectors are connected to the charging connectors of the electric vehicle, communicate with the vehicle controller, and receive receiving side voltage data indicating a change of the receiving side voltages with respect to time from the vehicle controller;
by temporarily varying a change rate of the detected supply voltage values with respect to time, generate a first feature point corresponding the varying of the change rate in the processed supply voltage data at a first time, and generate a second feature point corresponding the varying of the change rate in the receiving side voltage data at a second time;
calculate a time lag between the first time and the second time;
calculate a voltage difference between the supply voltage and the receiving side voltage based on the time lag, the processed supply voltage data and the receiving side voltage data; and
cause the electric charger to terminate supplying the DC power to the electric vehicle after determining that a charge state of the electric vehicle has reached a determination value.
2. The electric charging system according to
wherein the supply-side processor is further configured to calculate a conduction resistance of the charging cable based on the voltage difference, and calculate a determination value base on the conduction resistance of the charging cable, and
wherein the conduction resistance is an electric resistance or an impedance of the charging cable.
3. The electric charging system according to
wherein the elongated portion of the charging cable comprises a communication line, and
wherein the receiving side voltage data are transmitted to the electric charger via the communication line in the charging cable.
4. The electric charging system according to
wherein the supply-side processor is configured to:
by temporarily raising a change rate of the detected supply voltage values with respect to time, generate a first peak in the processed supply voltage data as the first feature point at the first time, and generate a second peak in the receiving side voltage data as the second feature point at the second time.
5. The electric charging system according to
wherein the supply-side processor is configured to:
by temporarily raising a change rate of the detected supply voltage values with respect to time, generate a first inflection point in the processed supply voltage data as the first feature point at the first time, and generate a second inflection point in the receiving side voltage data as the second feature point at the second time.
6. The electric charging system according to
wherein the supply-side processor is configured to:
eliminate one or more noise effects in the detected supply voltage data, by
generating the processed supply voltage data by subjecting the detected supply voltage data to the filtering process.
7. A method for charging of an electric vehicle, comprising:
supplying DC power to the electric vehicle from the electric charging system according to
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The present application claims priority from Japanese Patent Application No. 2011-078295 filed on Mar. 31, 2011, the entire contents of which are hereby incorporated by reference.
The present invention relates to an electric charging system that connects an electric charger and an electric vehicle via a charging cable and charges an electric storage device mounted on the electric vehicle.
In recent years, electric vehicles that are equipped with an electric motor for propulsion have been under development. The electric vehicle is equipped with an electric storage device such as battery. Upon charging the electric storage device, a charging cable extending from an electric charger is connected to a charging port of the electric vehicle (see, for example, Japanese Unexamined Patent Application Publication No 2009-83670). Furthermore, in the field of hybrid electric vehicles that are equipped with an engine and an electric motor for propulsion, so called a plug-in type vehicle is under development whose electric storage device can be charged with an electric charger.
Since the charging cable has an electric resistance and an impedance, a voltage drop occurs in the charging cable during charging. Accordingly there is a discrepancy between a supply voltage of the electric charger and a receiving voltage of the electric vehicle, which makes it difficult to highly accurately determine a charge state of the electric charging device based on the supply voltage of the electric charger. Thus, the charge state of the electric charging device cannot be correctly recognized by the electric charger, which makes it difficult for the electric charger to properly perform charging control.
The present invention aims so prevent an electric charger from mistakenly determining a charge state and to properly perform charging control.
An aspect of the present invention provides an electric charging system that connects an electric charger and an electric vehicle via a charging cable and charges an electric storage device mounted on the electric vehicle, the electric charging system including: a resistance calculating unit for calculating a conduction resistance of the charging cable based on a voltage difference between a supply voltage of the electric charger and a receiving voltage of the electric vehicle; a drop calculating unit for calculating a voltage drop in the charging cable during charging based on the conduction resistance of the charging cable and the supply current of the electric charger; a charge state determining unit that determines a charge state of the electric storage device by comparing the supply voltage of the electric charger and a preset determination value; and a determination value updating unit for updating the determination value based on the voltage drop.
Preferably, the determination value updating unit should update the determination value by adding the voltage drop to a preset determination base value.
Preferably, the conduction resistance of the charging cable should be an electric resistance or an impedance of the charging cable.
Preferably, the resistance calculating unit, the drop calculating unit, the charge state determining unit and the determination value updating unit should be provided at the electric charger.
Preferably, the receiving voltage of the electric vehicle should be transmitted to the resistance calculating unit via a communication line in the charging cable.
Preferably, the electric charging system should include a supply-side processing unit for calculating supply voltage data by applying a predetermined filtering process so the supply voltage of the electric charger; a receiving-side processing unit for calculating receiving voltage data by applying a predetermined filtering process to the receiving voltage of the electric vehicle; a feature point, assigning unit for assigning a feature point to the supply voltage data and the receiving data by altering at least any one of the supply voltage of the electric charger, the supply current of the electric charger, the receiving voltage of the electric vehicle and a receiving current of the electric vehicle; a data synchronizing unit for synchronizing the supply voltage data and the receiving voltage data based on the feature point assigned to the supply voltage data and the receiving data; and a voltage difference calculating unit for calculating a voltage difference between the supply voltage of the electric charger and the receiving voltage of the electric vehicle.
Preferably, the feature point assigning unit should assign a feature point to the supply voltage data and the receiving voltage dada by altering the supply current of the electric charger or the receiving voltage of the electric vehicle.
Preferably, the data synchronizing unit should calculate a time lag between the supply voltage data and the receiving voltage data based on the feature point and synchronize the supply voltage data and the receiving voltage data based on the time lag.
According to the present invention, the determination value with which the supply voltage of the electric charger is to be compared is updated based on the voltage drop in the charging cable, thereby preventing the electric charger from mistakenly determine a charge state. As a result, the electric storage device can be properly charged so that a poor charge state thereof can be prevented.
An embodiment of the present invention will hereunder be described with reference to the drawings.
As shown in
As shown in
Since the charging cable 14 connected to the electric vehicle 11 has an electric resistance (conduction resistance) R, a voltage drop occurs in the charging cable 14 when the electric charger 12 supplies electric power to the electric vehicle 11. Thus, the supply voltage Vs and the receiving voltage Vr are different from each other by a voltage drop ΔVa in the charging cable 14. Since the supply voltage Vs of the electric charger and the receiving voltage of the battery do not agree with each other, it is difficult to assure a fully charged state of the battery 13 simply by continuing to charge until the supply voltage Vs reaches to the predetermined voltage.
In order to address this problem, the charging control unit 48, which serves as a resistance calculating unit, a drop calculating unit, a charge state determining unit and a determination value updating unit, calculates the voltage drop ΔVa of the charging cable 14 and also updates the determination value Xb with which the supply voltage of the electric charger is to be compared based on the voltage drop ΔVa. Specifically, the charging control unit 48 firstly calculates the electric resistance R of the charging cable 14 in order to calculate the voltage drop ΔVa. Upon the calculation of the electric resistance R, a voltage difference ΔV between the supply voltage Vs and the receiving voltage Vr is calculated. The electric resistance R is calculated using the voltage difference ΔV and the supply current Is (R=ΔV/Is). Note that the receiving current. Ir may alternatively be used instead of the supply current. Is. Furthermore, the electric resistance R is used here as the conduction resistance of the charging cable 14, but the present invention is not limited to this. If the charging cable 14 exhibits an impedance Z as the conduction resistance, the impedance Z may be used instead of the electric resistance R. In the above description, the electric resistance R is calculated using the receiving voltage Vr and the supply voltage Vs. In order to use the receiving voltage Vr and the supply voltage Vs detected by the voltage sensors 30 and 45, it is necessary to eliminate noise effects by applying a filtering process such moving averaging and weighted moving averaging.
A procedure will be hereunder explained for comparing the supply voltage data D based on the supply voltage Vs and the receiving voltage data Dr based on the receiving voltage Vr after synchronizing them so as to calculate the voltage difference ΔV between the supply voltage Vs and the receiving voltage Vr with a high degree of accuracy. Firstly, the charging control unit 48 performs a pre-charging mode for calculating the voltage difference ΔV between the supply voltage data Ds (the supply voltage Vs) and the receiving voltage data Dr (the receiving voltage Vr) in prior to a full-charging mode for charging the battery 13 to a fully-charged state.
Since the feature point α1 assigned to the supply voltage data Ds and the feature point α2 assigned to the receiving voltage Dr indicates a same timing, as described above, the charging control unit 48, which servers as a data synchronizing unit, measures a temporal distance between the feature points α1 and α2 to calculate a time lag T between the supply voltage data Ds and the receiving voltage data Dr due to the filtering process (for example, 0.5 seconds). Then, the supply voltage data Ds (β1 in
In the above explanation, the receiving voltage Vs is changed in accordance with the artificially-changed supply voltage Vs. However, the present invention is not limited to this. Alternatively, the receiving voltage Vr may be artificially changed and the supply voltage Vs may be changed in accordance with the artificially-changed receiving voltage Vr. In this case, the receiving voltage Vr can be artificially changed by temporarily actuating an electric load installed in the electric vehicle 11 such as an electric. Further, while the supply voltage Vs is temporarily raised and dropped in the above explanation, the present invention is not limited to this. Alternatively, the raised supply voltage Vs may be maintained. Furthermore, the supply voltage Vs and the receiving voltage vr are raised in the above explanation, the present invention is not limited to this. Alternatively, the supply voltage Vs and the receiving voltage vr may be lowered. Furthermore, while the above description uses inflection points of the supply voltage data Ds and the receiving voltage data Dr as the feature points α1 and α2, the present invention is not limited to this. Alternatively, a feature point may be set at a point at where a predetermined voltage change amount or a voltage change speed is exceeded (or undershot) or a point at where a predetermined voltage value is exceeded (or undershot). Furthermore, an inflection point may be identified by changing the supply current instead of the supply voltage. For example, the inflection point can be identified by monitoring a degree of rise in an operation where, for example, the supply current is raised to a predetermined current value in a relatively short time and then maintained.
When the electric resistance of the charging cable 14 is calculated in the pre-charging mode as described above, the charging control unit 48 calculates a voltage drop ΔVa of the charging cable 14 in the subsequent full-charging mode based on the supply current upon charging (ΔVa=Is×R). Then, based on the voltage drop ΔVa, the charging control unit 48 calculates the determination value Xb with which the supply voltage Vs is to be compared by adding the voltage drop ΔVa to a preset determination base value Xa (Xb=Xa+ΔVa).
The present invention is not limited to the aforementioned embodiment, and permits various modifications and alterations within the technical scope of the invention. In the above embodiment, the charging control unit 48 in the electric charger 12 serves as the resistance calculating unit, drop calculating unit, charge state determining unit, supply-side processing unit, receiving-side processing unit, feature point assigning unit, data synchronizing unit and voltage difference calculating unit. However, the present invention is not limited to this. For example, the vehicle control unit 33 in the electric vehicle 11 may serves as the resistance calculating unit, drop calculating unit, charge state determining unit, supply-side processing unit, receiving-side processing unit, feature point, assigning unit, data synchronizing unit and voltage difference calculating unit. Further alternatively, the charging control unit 48 and the vehicle control unit 33 may share the functions of the resistance calculating unit, drop calculating unit, charge state determining unit, supply-side processing unit, receiving-side processing unit, feature point assigning unit, data synchronizing unit and voltage difference calculating unit.
In the above description, the fully-charged state is reached when the SOC is 80%. However, the fully-charged state is affected by a designed usage range of the battery (an upper limit of the SOC) and thus is not limited to she case where the SOC is 80%. Further, moving averaging and weighted moving averaging are referred to as the filtering process for calculating the receiving voltage data Dr and the supply voltage data Ds, but the present invention is not limited to this. Furthermore, filtering may be applied in a hardware sense using an electric circuit or in a software sense using a program. Furthermore, the filtering process such as moving averaging may also be applied in the case where the supply current Is and the receiving current Ir detected by the current sensors 31 and 46 are used.
The illustrated electric vehicle 11 is an electric vehicle which only has the motor-generator 20 for propulsion, but may be a hybrid-type electric vehicle that includes a motor-generator and an engine for propulsion. Further, the battery 13 including a lithium-ion rechargeable battery, a nickel metal hydride rechargeable battery or the like is used as the electric storage device, but the present invention is not limited to this. Alternatively, a capacitor such as a lithium-ion capacitor and an electric double layer capacitor may be used as the electricity storage device. Furthermore, the electric charger 12 in the above explanation is a conductive-type charger whose charging cable 14 is equipped with the power supply connector 42 of contact type, but the present invention is not limited to this. Alternatively, an inductive-type charger may be used whose charging cable is equipped with a power supply connector of non-contact type.
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